The present invention relates to a method and apparatus for securing one flexible pipe to another flexible pipe in an end-to-end configuration. In particular, but not exclusively, the present invention relates to a method of joining lengths of flexible pipe together to form a pipeline whereby gases trapped in an annulus region of a flexible pipe in one part of the pipeline can be transmitted into a corresponding annulus region in another part or parts of the pipeline.
Un-bonded flexible pipe is well-known and there are many uses for which such flexible pipe may be utilised. For example, transmitting fluid such as a production fluid like oil or gas from one location to another. Such flexible pipe may be used for offshore purposes as well as onshore or over land purposes. Typically such flexible pipe includes an inner fluid retaining layer, often referred to as a liner or barrier layer, which helps prevent fluid flow radially outwards from the bore. This layer has an inner diameter defining a bore along which fluid can flow. One or more armour layers are typically formed around the fluid retaining layer. The armour layer or layers are typically, but not exclusively, formed by winding steel strip about the fluid retaining layer. The armour layer or layers provide pressure reinforcement to prevent burst through of the inner fluid retention layer as well as preventing collapse of the flexible pipe due to external pressures. Additionally the armour layer can provide tensile strength to resist longitudinal forces of either extension or contraction on the flexible pipe. The flexible pipe also typically includes an outer sheath which is arranged to prevent ingress of fluid and/or contaminants from an environment where the flexible pipe is located.
The region between the outer sheath and inner fluid retaining layer defines an annulus region extending along the length of the portion of flexible pipe in which the armour layer or layers are located. One well known problem associated with this annular layer is that gas which penetrates through the fluid retaining layer from the transported fluid collects in the annular region. Also where the flexible pipe is utilised in an environment including undesirable gas such gas can permeate through the outer sheath and likewise be trapped in the annulus region. The trapped gases can collect and on occasion can cause rupturing in the flexible pipe or can degrade performance of the flexible pipe over time in many known ways. For this reason gases trapped in the annulus of un-bonded flexible pipe require venting. This has been achieved in the past by securing adjacent portions of flexible pipe together in a way such that a gas pathway is formed between corresponding annulus regions in adjacent flexible pipes. One or more valves have then been used to vent the gases trapped at one or more predetermined locations. In the past the pathway between connected pipes has been provided by jumper tubes. The configuration of the jumper tubes used has in the past been determined by the mechanism by which portions of flexible pipe have been secured to one another in an end-to-end configuration. For example, when end fittings have been used jumper tubes have required vent holes to be machined in each end fitting so that the jumper tube can transmit gases from one pipe end past the end fittings to the other pipe end.
Over the entire length of a pipeline formed by two or more portions of flexible pipe connected together in an end-to-end configuration the gases that accumulate in the annulus space can thus be directed to one or both ends of the pipeline or to other locations where an exit valve is located.
Unfortunately such jumper tubes are often fragile and tend to create obstructions when performing rehabilitation work. Broken jumper tubes or missing plugs in an end fitting can cause harmful gases to escape in an uncontrolled fashion or allow moisture into the flexible pipe annulus which potentially damages the flexible pipe and degrades performance.